Semiconductor wafer
A semiconductor wafer is disclosed for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer. The semiconductor wafer includes a formation member and a scribe groove located on the formation member according to an irradiation position of the laser beam. The scribe groove defines an open end and a bottom end. A width of the scribe groove is greater at the open end than at the bottom end.
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The following is based on and claims the benefit of Japanese Patent Application No. 2005-331217, filed Nov. 16, 2005 and Japanese Patent Application No. 2006-237632, filed Sep. 1, 2006, each of which are incorporated herein by reference.
FIELDThis invention relates to a semiconductor wafer and, more particularly relates to a semiconductor wafer in which irradiation of a laser beam forms a modified region by multiphoton absorption for dicing.
BACKGROUNDVarious methods have been proposed for dicing a semiconductor wafer. For instance, Japanese Patent Publication No. 2003-338468A discloses a method of dicing a wafer starting from a modified region formed by multiphoton absorption. The multiphoton absorption is caused by irradiation of a laser beam in the interior of the wafer.
For instance, as illustrated in
More specifically, in the case where the wafer 120 has a multilayer structure of an SOI (Silicon On Insulator) constructed with a lamination of a semiconductor substrate 121, an embedded layer of an oxide 122 (BOX; Buried OXide), and a single-crystal silicon layer 123, or the like, the refractive index to the laser beam differs depending on thickness and material of each layer due to differences in optical properties of each layer. For this reason, a laser beam is likely to reflect or scatter in a boundary surface of layers of different refractive indices, etc. (e.g., a boundary surface between the embedded oxide layer 122 and the single-crystal silicon layer 123). Accordingly, the scribe groove 125 is formed along the predetermined dicing line DL in the case of the wafer 120. Since a part of the single-crystal silicon layer 123 is removed, it becomes possible to form focal points P1, P2 of the laser beams L1, L2 along an optical axis J at either a shallow position (i.e., a position near the surface 120a) of the semiconductor substrate 121 or a deep position (i.e., a position near the opposite side 120b).
The scribe groove 125 is set to have the same width in a direction perpendicular to the predetermined dicing line DL. Accordingly, a wall 125c that joins the opening 125a to the bottom 125b is provided approximately at a right angle (i.e., θa=90°) with respect to the outer surface 120a and the bottom 125b. For this reason, if the chips diced by the laser (i.e., semiconductor chips) rub against each other, an angle part 120c that forms the opening 125a of the scribe groove 125 can chip off, resulting in degradation in quality of the chips.
SUMMARYA semiconductor wafer is disclosed for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer. The semiconductor wafer includes a formation member with an outer surface. The semiconductor wafer also includes a scribe groove located on the formation member according to an irradiation position of the laser beam. The scribe groove includes a side wall that is planar and that is provided at a tilt angle with respect to the outer surface of the formation member. The tilt angle is the smallest angle between the side wall and the outer surface, and the tilt angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
Furthermore, a semiconductor wafer is disclosed for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer. The semiconductor wafer includes a formation member with an outer surface and a scribe groove located on the formation member according to an irradiation position of the laser beam. The scribe groove includes a side wall that is curved such that a tangent angle is defined between a tangent line of the side wall and the outer surface of the formation member. The tangent angle is the smallest angle between the tangent line and the outer surface, and the tangent angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
Moreover, a semiconductor wafer is disclosed for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer. The semiconductor wafer includes a formation member and a scribe groove located on the formation member according to an irradiation position of the laser beam. The scribe groove defines an open end and a bottom end. A width of the scribe groove is greater at the open end than at the bottom end.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring initially to
Although not illustrated in this wafer 20, a plurality of chips formed through a diffusion process and the like are aligned and arranged in rows and columns. A dicing line DL is illustrated in a predetermined location along which the chips are diced away from the wafer by laser dicing. Also, expand tape (not shown) is glued to substantially all of a reverse side 20b of the wafer 20. It will be appreciated that the dicing line DL is a virtual line (i.e., a line does not exist actually on an outer surface 20a of the wafer 20).
The irradiation of laser beams L1, L2 onto the predetermined dicing line DL makes it possible to form a modified region K by multiphoton absorption in the interior of the semiconductor substrate 21. The wafer 20 can be separated into a plurality of chips by being diced starting from this modified region K. More specifically, dicing occurs starting at the modified regions K via a tension force. The tension force is generated, for example, by pulling the expand tape on the reverse side 20b toward an outer radial direction of the wafer and pressurizing the wafer 20 from the reverse side 20b.
Thus, the laser beams L1, L2 are irradiated along the predetermined dicing line DL and the modified region K is formed in the interior of the wafer when the dicing is performed. The laser beams L1, L2 are focused according to a convergence angle α. More specifically, the convergence angle α is the angle of the condenser lens for focusing the laser beams L1, L2.
The wafer 20 is multilayered by an SOI structure, and each layer can have a different refractive index for the laser beams L1, L2 depending on its thickness and material. As such, the laser beam can generate reflection and scattering at a boundary surface between, for example, the embedded oxide layer 22 and the single-crystal silicon layer 23. Therefore, the wafer 20 of this embodiment is provided with a scribe groove 25 therein. The scribe groove 25 is provided in a formation member of the wafer 20. In the embodiment shown, the formation member is the single-crystal silicon layer 23; however, it will be appreciated that the scribe groove 25 could be any suitable formation member other than the single-crystal layer 23. In the embodiment shown, the scribe groove 25 is formed by removing a portion of the single-crystal silicon layer 23 on the predetermined dicing line DL, which could otherwise hinder the laser beams L1, L2 from forming focal points P1, P2.
The scribe groove 25 is a linear groove with an axis extending along the predetermined dicing line DL. The depth of the scribe groove 25 extends from the outer surface 20a toward the embedded oxide layer 22 so as to define two side walls 25c extending between the outer surface 20a and the embedded oxide layer 22. The two side walls 25c are separated at a distance across the width of the scribe groove 25. It is understood that the embedded oxide layer 22 is the bottom surface 25b of the scribe groove 25. In the depth direction, a bottom end 28 of the scribe groove 25 reaches the embedded oxide layer 22, and an open end 29 of the scribe groove 25 is adjacent the surface 20a. The width of the scribe groove 25 extends perpendicular to the dicing line DL.
The scribe groove 25 has a cross-sectional trapezoidal shape closing toward the embedded oxide layer 22. In other words, the width of the scribe groove 25 at the bottom end 28 is less than the width of the scribe groove 25 at the open end 29. Furthermore, the walls 25c are substantially planar. Also, the walls 25c are provided at an obtuse angle θ1 (90°<θ1<180°) with respect to the outer surface 20a of the wafer 20. In other words, the angle θ1 is the smallest angle between the respective wall 25c and the outer surface 20a, and yet the angle θ1 is an obtuse angle.
In one embodiment, the scribe groove 25 is formed, for example, by chemical processing, such as wet etching and dry etching, or by mechanical processing, such as cutting with a dicing blade etc. and irradiation of a laser beam. Moreover, the bottom surface 25b of the scribe groove 25 is substantially flat and smooth to thereby suppress reflection and scattering of the laser beams L1, L2.
As such, an angle part 20c at an obtuse angle is defined by the wall 25c and the surface 20a on the predetermined dicing line DL. Since the angle part that forms the scribe groove 25 of the chip obtained by dicing it from the wafer 20 ultimately has an obtuse angle, the angle part is resistant to chipping as compared with the prior art where the angle part is at a right angle or an acute angle.
The wall 25c of the scribe groove 25 is formed so as to form a flat slope having a tilt angle θ1. In one embodiment, the tilt angle θ1 equals approximately half of the convergence angle a plus ninety degrees (as viewed on a plane). That is:
θ1=α/2+90°
Thus, the wall surface of a wall 25c can be made almost parallel to fringe contour lines of the laser beams L1, L2 focused by the condenser lens. As such, even if the condenser lens is brought close to the surface 20a of the wafer 20, it is possible to form the focal point P2 at a deep position of the semiconductor substrate 21 while the single-crystal silicon layer 23 does not interrupt propagation of the focused laser beam L2.
In the wafer 20 according to this embodiment, it becomes possible for a dicing machine DM (
As shown in
Because of formation of the scribe groove 25, the laser beam L2 is irradiated onto the bottom 25b of the scribe groove 25 as an entrance plane and not onto the single-crystal silicon layer 23 as an entrance plane. Thus, reflection and scattering of the laser beam L2 can be better controlled and it becomes possible to form the focal point P2 at a predetermined deep position of the semiconductor substrate 21 and form a modified region at this deep position.
Furthermore, as shown in
Since the scribe groove 25 is formed and the single-crystal layer in the surface 20a is removed, the laser beam L1 is irradiated onto the bottom 25b of the scribe groove 25 as an entrance plane and not onto the single-crystal silicon layer 23 as an entrance plane, there is no boundary surface between the single-crystal silicon layer 23 and the embedded oxide layer 22 in a region where the laser beam L1 is irradiated. Therefore, reflection and scattering of the laser beam L1 at the boundary surface can be better controlled. A focal point is located at a predetermined shallow position of the semiconductor substrate 21 (i.e., adjacent the surface 20a) and the modified region K is formed.
It is noted that, in the boundary surface between the scribe groove 25 (i.e., air) and the embedded oxide layer 22, there is substantially zero refraction of the laser beams L1, L2. Accordingly, the laser beams L1, L2 irradiated onto the bottom 25b is transmitted in the embedded oxide layer with a transmittance of approximately 100%.
In one embodiment, when the focal point P2 is located at a deep position of the semiconductor substrate 21 (i.e., adjacent the reverse side 20b) with the condenser lens disposed closer to the surface 20a, a laser beam diameter W2 is set to be smaller than a scribe width W1 (i.e., the width of the bottom end 28 of the scribe groove 25). Moreover, as shown in
In another embodiment shown in
Furthermore, in an embodiment illustrated in
More specifically, in the embodiment of
Furthermore, since the tilt angle 01 of the opening-side wall 25c1 is similar to the tilt angle θ1 of the scribe groove 25 shown in
In the embodiment of
In the embodiment of
Thus, in the embodiments of
Moreover, the fringe contour line of the laser beams L1, L2 focused by the condenser lens can be made approximately parallel to the wall surface of the wall 25c, 45c even if the condenser lens is brought close to the surface 20a (40a) of the wafer 20 (40). Thus, the single-crystal silicon layer 23 is unlikely to hinder the focused laser beams L1, L2 from propagating and the focal point P2 can be formed at a deep position of the semiconductor substrate 21.
In the embodiments of
Referring now to
As shown in
A scribe groove 55 formed in the wafer 50 is also included. The scribe groove 55 is a linear long groove formed along the predetermined dicing line DL, having a sufficient depth to reach the embedded oxide layer 22. The width of the scribe groove 55 at an open end 59 is greater than a width of the scribe groove 55 at a bottom end 58. With this formation, the wall 55c that joins the opening of the scribe groove 55 to the bottom 55b of the scribe groove 55 has a curved shape such that “R-chamfering” is processed on an angle part 50c of the surface 50a of the wafer 50. This scribe groove 55 is formed, in one embodiment, by chemical processing using wet etching, dry etching, by mechanical processing by cutting with a dicing blade, etc., or irradiation of the laser beam. Moreover, the bottom 55b thereof is formed to be such a flat smooth surface as generates neither reflection nor scattering of the laser beams L1, L2.
With this formation, since the tangent angle θ2 that the tangent line of the wall 55c makes with the surface 50a of the predetermined dicing line DL can be made to be an obtuse angle, the angle part 50c can be rounded. Since the angle part that forms the scribe groove 55 of the chip obtained by dicing it from the wafer 50 is also rounded, the angle part is more resistant to chipping as compared with the case where the angle part is of a right angle or acute angle.
In the embodiment shown in
Thus, since the angle part that forms the scribe groove 55 of the chip obtained by dicing it from the wafer 50 is also rounded, the angle part is resistant to chipping. Therefore, since the angle part is unlikely to chip off even if the chips rub against each other, the wafer 50 can reduce degradation in quality of the chips diced therefrom.
In the each embodiment described above, the embedded oxide layer and the single-crystal silicon layer are exemplified as the formation layer on the wafer located adjacent the surface of the predetermined position onto which the laser beam is irradiated. However, it will be appreciated that these layers could be otherwise embodied.
Referring for instance to
As shown in
The scribe groove 65 is included between the caps 62 like this arranged side by side across the predetermined dicing line DL. Each of the caps 62 is formed in such a way that its lateral face 62a becomes a wall 65c that extends from the outer surface 60a to a bottom 65b of the scribe groove 65. The wall 65 makes an obtuse angle θ1 (90°<θ1<180°) with the outer surface 60a of the wafer 60. In
Thus, since the angle part can be made resistant to chipping off as compared with the case where the angle part (angle part of the cap 62) is of a right angle or acute angle, the angle part (angle part of the cap 62) is unlikely to chip off even if the chips like this rub against each other. Accordingly, degradation in quality of the chip is less likely.
As shown in
Moreover, as shown in
Thus, the angle part of the cap 62″ is unlikely to chip off even if the chips like this rub against each other. Therefore, degradation in quality of the chip can be reduced.
Furthermore, as shown in the embodiments of
As shown in
An opening 75a between adjacent passivation films 72 functions as the scribe groove 75. The side wall 75c of the scribe groove 75 is provided at an obtuse angle θ1 (90°<θ1<180°) with respect to an outer surface 70a of the wafer 70. In
As shown in
In the embodiment of
Moreover, the formation member for the scribe groove may be a part of a heterojunction structure that forms a heterojunction in conjunction with the semiconductor substrate (i.e., a formation member on the wafer) as shown in the embodiments of
As shown in
Moreover, in the embodiment shown in
Furthermore, as shown in
In another embodiment illustrated in
Several of the above-mentioned embodiments include a multilayer substrate of an SOI structure composed of a semiconductor substrate, an embedded oxide layer, and a single-crystal silicon layer as a semiconductor wafer. However, the SOI structure may be replaced with a SIMOX (Silicon, IMplanted OXide), and a semiconductor material may be SiC, ZnO, AIN, GaAs, or the like, for example. The adoption of these modifications gives the same action and effects as described above.
Furthermore, the semiconductor wafer according to this invention can be applied to the case where a workpiece that is formed by MEMS (Micro Electro Mechanical Systems), for example, an acceleration sensor, a gyrosensor, an image sensor, etc. are constructed on the semiconductor wafer, and such applications can attain the same action and effects as the embodiments described above.
While only the selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the disclosure as defined in the appended claims. Furthermore, the foregoing description of the embodiments herein is provided for illustration only, and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.
Claims
1. A semiconductor wafer for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer, the semiconductor wafer comprising:
- a formation member with an outer surface; and
- a scribe groove located on the formation member according to an irradiation position of the laser beam, the scribe groove including a side wall that is planar and that is provided at a tilt angle with respect to the outer surface of the formation member,
- wherein the tilt angle is the smallest angle between the side wall and the outer surface, and wherein the tilt angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
2. A semiconductor wafer for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer, the semiconductor wafer comprising:
- a formation member with an outer surface; and
- a scribe groove located on the formation member according to an irradiation position of the laser beam, the scribe groove including a side wall that is curved such that a tangent angle is defined between a tangent line of the side wall and the outer surface of the formation member,
- wherein the tangent angle is the smallest angle between the tangent line and the outer surface, and wherein the tangent angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
3. A semiconductor wafer for which irradiation of a laser beam forms a modified region due to multiphoton absorption to thereby facilitate dicing of the semiconductor wafer, the semiconductor wafer comprising:
- a formation member; and
- a scribe groove located on the formation member according to an irradiation position of the laser beam, the scribe groove defining an open end and a bottom end,
- wherein a width of the scribe groove is greater at the open end than at the bottom end.
4. The semiconductor wafer of claim 3, wherein the formation member includes an outer surface,
- wherein the scribe groove includes a side wall that is planar and that is provided at a tilt angle with respect to the outer surface of the formation member,
- and wherein the tilt angle is the smallest angle between the side wall and the outer surface, and wherein the tilt angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
5. The semiconductor wafer of claim 3, wherein the formation member includes an outer surface,
- wherein the scribe groove includes a side wall that is curved such that a tangent angle is defined between a tangent line of the side wall and the outer surface of the formation member,
- and wherein the tangent angle is the smallest angle between the tangent line and the outer surface, and wherein the tangent angle is between ninety degrees (90°) and one hundred eighty degrees (180°).
6. The semiconductor wafer of claim 3, wherein the formation member is an outer layer and an embedded layer such that the depth of the scribe groove extends into the outer layer and the embedded layer.
7. The semiconductor wafer of claim 3, wherein the formation member includes an outer surface,
- wherein the scribe groove includes a side wall that includes an opening-side wall adjacent the open end and a bottom-side wall adjacent the bottom end,
- wherein the open-side wall is planar and provided at a tilt angle with respect to the outer surface of the formation member,
- wherein the tilt angle is the smallest angle between the opening-side wall and the outer surface, wherein the tilt angle is between ninety degrees (90°) and one hundred eighty degrees (180°), and
- wherein the bottom-side wall is approximately perpendicular to the outer surface of the formation member.
8. The semiconductor wafer of claim 3, wherein the formation member includes an outer surface,
- wherein the scribe groove includes a side wall that includes an opening-side wall adjacent the open end and a bottom-side wall adjacent the bottom end,
- wherein the open-side wall is curved such that a tangent angle is defined between a tangent line of the open-side wall and the outer surface of the formation member,
- wherein the tangent angle is the smallest angle between the tangent line and the outer surface, wherein the tangent angle is between ninety degrees (90°) and one hundred eighty degrees (180°), and
- wherein the bottom-side wall is approximately perpendicular to the outer surface of the formation member.
9. The semiconductor wafer of claim 3, wherein the formation member is a member chosen from a group consisting of a cap that protects a substrate of the semiconductor wafer, a passivation film, a heterojunction structure, and an electrode pad.
10. The semiconductor wafer of claim 3, wherein the width of the scribe groove at the bottom end is greater than a diameter of the laser beam.
11. The semiconductor wafer of claim 4, wherein the laser beam is focused according to a convergence angle, and wherein the tilt angle is approximately equal to half of the convergence angle plus ninety degrees (90°).
12. The semiconductor wafer of claim 5, wherein the tangent angle is approximately equal to half of the convergence angle plus ninety degrees (90°).
Type: Application
Filed: Nov 16, 2006
Publication Date: May 17, 2007
Applicant: DENSO CORPORATION (Kariya-city)
Inventors: Yumi Maruyama (Kariya-city), Tetsuo Fujii (Toyohashi-city)
Application Number: 11/600,099
International Classification: H01L 21/00 (20060101); H01L 23/544 (20060101);